Automatic transmission

ABSTRACT

An automatic transmission capable of causing first and second clutches and a connection/disconnection device to properly operate during stoppage of a vehicle, thereby enabling preventing vibration and improving marketability as well as obtaining excellent vehicle startability. When a shift position is switched to a forward travel position, first and second connection operations are executed for connecting transmission of a motive power of a prime mover, from first and second gear mechanisms to drive wheels, respectively, while changing the speed thereof. If the shift position is switched to the forward travel position and no request for a standing start of the vehicle is determined to be made by a driver, engagement of first and second gear clutches for connecting/disconnecting between the prime mover and the gear mechanisms is permitted when both the first and second connection operations have been completed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic transmission thattransmits motive power of a prime mover in a state in which the speed ofthe motive power is stepwise changed, and more particularly to anautomatic transmission including first and second gear mechanismsprovided separately from each other.

2. Description of the Related Art

Conventionally, as an automatic transmission of this kind, one disclosedin the Publication of Japanese Patent No. 4875384 is known. Thisautomatic transmission is used for transmitting motive power of aninternal combustion engine, which is a motive power source of a vehicle,in a state in which the speed of the motive power is stepwise changed,to a drive shaft, and is comprised of a first gear mechanism, a secondgear mechanism, a first clutch, a second clutch, and a shift device. Thefirst gear mechanism includes a first drive gear group formed by a firstmain shaft connected to the engine, a transmission output shaft thatextends in parallel with the first main shaft and is connected to thedrive shaft, and a first drive gear group formed by a plurality of gearsrotatably provided on the first main shaft, and a first driven geargroup formed by a plurality of gears that are fixed to the transmissionoutput shaft and are in mesh with the gears of the first drive geargroup, respectively. Gear trains of a first speed position, a thirdspeed position, and a fifth speed position are formed by the first drivegear group and the first driven gear group. The first clutch is ahydraulic multiple-disc clutch which is engaged and disengaged tothereby connect and disconnect between the engine and the first mainshaft.

Further, the second gear mechanism is configured similarly to the firstgear mechanism, and includes a second main shaft connected to theengine, the transmission output shaft, a second drive gear group formedby a plurality of gears fixed to the second main shaft, and a seconddriven gear group formed by a plurality of gears that are rotatablyprovided on the transmission output shaft and are in mesh with the gearsof the second drive gear group, respectively. As described above, thetransmission output shaft is shared as an output shaft by the first andsecond gear mechanisms. Further, gear trains of a second speed positionand a fourth speed position are formed by the second drive gear groupand the second driven gear group. The second clutch is a hydraulicmultiple-disc clutch which is engaged and disengaged to thereby connectand disconnect between the engine and the second main shaft.Furthermore, the shift device is capable of executing an operation forconnecting one of the gears of the first drive gear group to the firstmain shaft, and an operation for connecting one of the gears of thesecond driven gear group to the transmission output shaft.

In the conventional automatic transmission configured as above, when ina neutral state in which neither the first drive gear group nor thesecond driven gear group is connected, the first and second clutches aredisengaged. Further, for the standing start of the vehicle, one of thegears of the first drive gear group for the first speed position isconnected to the first main shaft by the shift device, and upon thelapse of a predetermined time period after completion of the connection,the first clutch is engaged.

Further, it is envisaged that in an automatic transmission, such as theabove-described conventional automatic transmission, which includes thefirst and second gear mechanisms and the first and second clutches,during stoppage of the vehicle, there is performed the following controloperation: During stoppage of the vehicle, when the shift position of ashift lever is located at a parking position or a neutral position, thefirst and second clutches are disengaged, whereby the engine isdisconnected from the first and second gear mechanisms, and theconnection of gears in the first and second gear mechanisms is released(neutral state).

Further, during stoppage of the vehicle, in a case where the shiftposition has been switched to a drive position, if a request for thestanding start of the vehicle has not been made by the driver, toquickly start the vehicle in response to a request made afterward forthe standing start of the vehicle, in the second gear mechanism, a gearfor the second speed position is connected beforehand to thetransmission output shaft as a gear for the standing start of thevehicle, while the second clutch is controlled to a half-clutch statewithout being completely engaged, and the first clutch is disengaged. Inthis case, it is envisaged that with a view to quickly transmitting alarger torque to the drive wheels at the standing start of the vehicleperformed afterwards, to make it possible to quickly transmit motivepower of the engine to the drive wheels at a transmission gear ratio ofthe first speed position, not only the gear for the second speedposition is connected beforehand to the transmission output shaft butalso the gear of the first gear mechanism for the first speed positionis connected beforehand to the main shaft.

In a case where the control operation as described above (hereinafterreferred to as the “during-stoppage control operation”) is performed,for example, when wet multiple-disc clutches to which lubricating oil issupplied are used as the first and second clutches, there arise thefollowing problems: The clutches of this kind are in a slightly engagedstate even when they are completely disengaged, since the transmissionof the motive power is not completely disconnected due to frictionbetween friction plates of the clutches and lubricating oil (hereinafterreferred to as the “clutch friction”). The clutch friction becomeslarger as the amount of lubricating oil supplied to the clutches islarger, whereby the motive power transmitted via the clutches becomeslarger. Further, in general, the amount of supplied lubricating oilbecomes larger as the degree of engagement of the clutches is larger,since friction plates of the clutches have to be cooled by thelubricating oil.

To solve the above-described problems, in the during-stoppage controloperation described above, e.g. when the second clutch is controlled tothe half-clutch state before completion of connection of the gear forthe first speed position, the amount of lubricating oil supplied to thefirst and second clutches becomes larger according to the controloperation, whereby the clutch friction of the two clutches becomeslarger, which in turn increases the motive power transmitted from theengine to the first and second main shafts via the first and secondclutches. On the other hand, the vehicle is at a stop, whereby therotational speed of the gear for the first speed position connected tothe drive wheels is equal to 0, and hence connection of the gear for thefirst speed position and the first main shaft is performed in a state inwhich a relatively large differential rotation occurs therebetween. Thiscauses large vibration even though the vehicle is at a stop, resultingin the degraded marketability. Such problems can similarly occur alsowhen the first clutch is controlled to the half-clutch state beforecompletion of connection of the gear for the second speed position inthe during-stoppage control operation.

Further, there is a fear that the problems as described above occur alsowhen dry multiple-disc clutches to which lubricating oil is not suppliedor electromagnetic clutches are used as the first and second clutches.More specifically, one of the first and second clutches is sometimes notcompletely disengaged immediately after stoppage of the vehicle. In sucha case, the motive power of the engine is transmitted to the one of thefirst and second main shafts, to cause the same to rotate. As aconsequence, in this case as well, connection of the gear for the firstspeed position (gear for the second speed position) and the first mainshaft (transmission output shaft) is performed in a state in which arelatively large differential rotation occurs therebetween. This canresult in generation of large vibration and degraded marketability.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an automatictransmission which is capable of causing first and second clutches and aconnection/disconnection device to properly operate during stoppage of avehicle, whereby it is possible not only to prevent vibration andimprove marketability but also to obtain excellent startability of avehicle.

To attain the above object, the present invention provides an automatictransmission for transmitting motive power of a prime mover to drivewheels of a vehicle in a state in which a speed of the motive power isstepwise changed, comprising a first gear mechanism that is connected tothe prime mover and the drive wheels, for transmitting the motive powerof the prime mover to the drive wheels in a state in which the speed ofthe motive power is changed at a transmission gear ratio of one speedposition of a first speed position group composed of a plurality ofspeed positions, a first clutch that is engaged/disengaged to therebyconnect/disconnect between the prime mover and the first gear mechanism,a second gear mechanism that is disposed in parallel with the first gearmechanism, and is connected to the prime mover and the drive wheels, fortransmitting the motive power of the prime mover to the drive wheels ina state in which the speed of the motive power is changed at atransmission gear ratio of one speed position of a second speed positiongroup composed of a plurality of speed positions, a second clutch thatis engaged/disengaged to thereby connect/disconnect between the primemover and the second gear mechanism, control means for controlling thefirst and second clutches, a connection/disconnection device that isprovided in the first and second gear mechanisms, and is capable ofexecuting a first connection operation for selecting one speed positionfrom the first speed position group and connecting transmission ofmotive power from the first gear mechanism to the drive wheels, usingthe selected one speed position, a first disconnection operation fordisconnecting the transmission of the motive power, a second connectionoperation for selecting one speed position from the second speedposition group and connecting transmission of motive power from thesecond gear mechanism to the drive wheels, using the selected one speedposition, and a second disconnection operation for disconnecting thetransmission of the motive power, shift position-detecting means fordetecting a shift position of a shift lever selectively operated by adriver of the vehicle to one of a plurality of shift positions includinga non-traveling position for stoppage of the vehicle, and a forwardtravel position for forward travel of the vehicle, and determinationmeans for determining whether or not a request for a standing start ofthe vehicle has been made by the driver, wherein when the detected shiftposition is at the non-traveling position, the control means disengagesthe first and second clutches, wherein thereafter, when the shiftposition is switched from the non-traveling position to the forwardtravel position, the connection/disconnection device executes the firstand second connection operations, and in the second connectionoperation, selects a predetermined standing start speed position for thestanding start of the vehicle from the second speed position group, andwherein in a case where the shift position is switched to the forwardtravel position, and also it is determined that the request for thestanding start of the vehicle has not been made by the driver, when boththe first and second connection operations have been completed, thecontrol means permits engagement of the first and second clutches.

With the configuration of this automatic transmission, the first andsecond gear mechanisms are arranged in parallel with each other, and areconnected to the prime mover and the drive wheels of the vehicle. Thespeed of the motive power transmitted from the prime mover via the firstgear mechanism is changed at the transmission gear ratio of one of thespeed positions of the first speed position group, and the speed of themotive power transmitted from the prime mover via the second gearmechanism is changed at the transmission gear ratio of one of the speedpositions of the second speed position group. Further, the first clutchis engaged and disengaged to thereby connect and disconnect between theprime mover and the first gear mechanism, and the second clutch isengaged and disengaged to thereby connect and disconnect between theprime mover and the second gear mechanism. Furthermore, theconnection/disconnection device provided in the first and second gearmechanisms executes the first connection operation for selecting onespeed position from the first speed position group and connecting thetransmission of the motive power from the first gear mechanism to thedrive wheels, using the selected one speed position, the firstdisconnection operation for disconnecting the transmission of the motivepower, the second connection operation for selecting one speed positionfrom the second speed position group and connecting the transmission ofthe motive power from the second gear mechanism to the drive wheels,using the selected one speed position, and the second disconnectionoperation for disconnecting the transmission of the motive power.

Further, when the shift position of the shift lever is at thenon-traveling position, the first and second clutches are disengaged tothereby disconnect between the prime mover and the first and second gearmechanisms. Furthermore, when the shift position is switched from thenon-traveling position to the forward travel position, the first andsecond connection operations are executed by theconnection/disconnection device, whereby the transmission of the motivepower from the first and second gear mechanisms to the drive wheels isconnected. Further, in the case where the shift position is switched tothe forward travel position, when it is determined that a request forthe standing start of the vehicle has not been made by the driver, i.e.during stoppage of the vehicle, the engagement of the first and secondclutches which have been in a disengaged state before that time ispermitted after completion of the first and second connectionoperations. In other words, the engagement of the first and secondclutches is inhibited up to completion of the first and secondconnection operations.

With this operation, during stoppage of the vehicle, differently fromthe during-stoppage control operation as described hereinabove, neitherthe first connection operation nor the second connection operation isexecuted during or after completion of an engagement operation of one ofthe first and second clutches. Therefore, it is possible to avoidexecution of the first and second connection operations in a state inwhich a large differential rotation is generated between portions of thefirst and second gear mechanisms, connected to the prime mover, andportions of the two gear mechanisms, connected to the drive wheels,which in turn prevents vibration from being caused by executing thefirst and second connection operations, thereby making it possible toimprove marketability.

In this case, the first and second connection operations are executedbeforehand when the shift position has been switched to the forwardtravel position. Further, the predetermined standing start speedposition for the standing start of the vehicle is selected from thesecond speed position group as a speed position for use in the secondconnection operation. From the above, at the subsequent standing startof the vehicle, torque of the prime mover can be transmitted to thedrive wheels quickly via one of the first and second clutches and one ofthe first and second gear mechanisms, associated with the one of thefirst and second clutches, and therefore it is possible to obtain theexcellent startability of the vehicle. As described above, according tothe present invention, it is possible to cause the first and secondclutches and the connection/disconnection device to properly operateduring stoppage of the vehicle, thereby making it possible not only toprevent vibration and improve marketability but also to obtain excellentstartability of the vehicle.

Preferably, the connection/disconnection device selects a speed positionwith a transmission gear ratio larger than a transmission gear ratio ofthe predetermined standing start speed position, from the first speedposition group, as a speed position for use in the first connectionoperation executed when the shift position has been switched to theforward travel position, and the automatic transmission furthercomprises required torque-calculating means for calculating a requiredtorque required for the drive wheels, wherein in a case where the shiftposition has been switched to the forward travel position, and also itis determined that the request for the standing start of the vehicle hasbeen made by the driver, when both the first and second connectionoperations have been completed, the control means selects and engagesone of the first and second clutches and disengages the other of thefirst and second clutches, based on the calculated required torque.

With the configuration of the preferred embodiment, the speed positionwith the transmission gear ratio larger (on a lower-speed side) than thetransmission gear ratio of the standing start speed position is selectedfrom the first speed position group, as the speed position for use inthe first connection operation executed when the shift position has beenswitched to the forward travel position. With this operation, theincreasing degree of torque by the first gear mechanism becomes largerthan that of torque by the second gear mechanism. Further, the requiredtorque required for the drive wheels is calculated by the requiredtorque-calculating means.

Further, in the case where the shift position has been switched to theforward travel position, and it is determined that the request for thestanding start of the vehicle has been made by the driver, when both thefirst and second connection operations have been completed, one of thefirst and second clutches is selected and engaged, and the other of thefirst and second clutches is disengaged, based on the calculatedrequired torque. With this operation, at the standing start of thevehicle, the torque of the prime mover can be transmitted to the drivewheels using one of the first and second gear mechanisms, associatedwith the selected one of the clutches, in a state in which the torque ofthe prime mover is increased to meet the required torque.

Preferably, the first and second clutches are formed by wet clutchesthat use lubricating oil, and the automatic transmission furthercomprises a lubricating oil supply system that supplies lubricating oilto the first and second clutches, and is capable of changing alubricating oil supply amount, which is an amount of lubricating oilsupplied to the first and second clutches, wherein when one of the firstand second clutches is engaged, the lubricating oil supply system setsthe lubricating oil supply amount to a first predetermined amount,whereas when both of the first and second clutches are disengaged, thelubricating oil supply system sets the lubricating oil supply amount toa second predetermined amount smaller than the first predeterminedamount.

With the configuration of the preferred embodiment, the lubricating oilsupply amount, which is the amount of lubricating oil supplied to thefirst and second clutches, is changed by the lubricating oil supplysystem. The first and second clutches are formed by so-called wetclutches, and hence even during disengagement of the clutches, when thelubricating oil supply amount is large, again, clutch friction becomeslarger, as described hereinabove, whereby the motive power transmittedfrom the prime mover to the respective first and second gear mechanismsvia the first and second clutches becomes larger. As a consequence,there can arise a problem of the above-described first and secondconnection operations, i.e. a problem that large vibration is generatedand marketability is degraded.

With the above-described configuration, when one of the first and secondclutches is engaged, the lubricating oil supply amount is set to thefirst predetermined amount, whereas when both of the first and secondclutches are disengaged, the lubricating oil supply amount is set to thesecond predetermined amount, which is set to a value smaller than thefirst predetermined amount. This makes it possible to prevent theabove-described problem from occurring, since clutch friction causedwhen both the first and second clutches are disengaged can besuppressed.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a skeleton diagram of an automatic transmission according toan embodiment of the present invention and a vehicle to which theautomatic transmission is applied;

FIG. 2 is a block diagram of an ECU etc. of the automatic transmission;

FIG. 3 is a schematic view of a lubricating oil supply system of theautomatic transmission;

FIG. 4 is a flowchart of an in-gear control process executed by the ECU;

FIG. 5 is a flowchart of a clutch control process executed by the ECU;

FIG. 6 is a flowchart of a lubricating oil control process executed bythe ECU;

FIG. 7 is a timing diagram showing an example of operation performed bythe automatic transmission;

FIG. 8 is a timing diagram showing a comparative example of theoperation shown in FIG. 7;

FIG. 9 is a timing diagram showing an example of operation performed bythe automatic transmission, different from the example shown in FIG. 7;and

FIG. 10 is a timing diagram showing an example of operation performed bythe automatic transmission, different from the examples shown in FIGS. 7and 9.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will now be described in detail with reference to thedrawings showing preferred embodiment thereof. A vehicle V shown in FIG.1 is a so-called hybrid vehicle, and is equipped with an internalcombustion engine (hereinafter referred to as the “engine”) 3 and anelectric motor (hereinafter referred to as the “motor”) 4 as motivepower sources, a pair of drive wheels DW (only one of which is shown),and a pair of driven wheels (not shown).

The engine 3 is a gasoline engine including a plurality of cylinders,and includes a crankshaft 3 a for outputting motive power, and fuelinjection valves (not shown) and spark plugs (not shown). The fuelinjection valves and the spark plugs are provided for the respectivecylinders. The operations of the fuel injection valves and the sparkplugs are controlled by an ECU 2 appearing in FIG. 2, whereby theoperating state of the engine 3 is controlled. Further, the motor 4 is abrushless DC motor, and includes an output shaft 4 a for outputtingmotive power. The operation of the motor 4 is controlled by the ECU 2.

An automatic transmission 1 according the present embodiment is used totransmit motive power of the engine 3 and the motor 4 to the drivewheels DW while stepwise changing the speed of the motive power.Specifically, the automatic transmission 1 is a so-called dual-clutchtype automatic transmission, and includes a first clutch 5, a secondclutch 6, a first gear mechanism GA1, a second gear mechanism. GA2disposed in parallel with the first gear mechanism GA1, a reversemechanism RA, a connection/disconnection mechanism, and the ECU 2 (seeFIG. 2).

The first clutch 5 is a wet multiple-disc clutch, and includes an outerclutch plate 5 a coaxially fixed to the crankshaft 3 a, an inner clutchplate 5 b coaxially fixed to one end of a first input shaft 11, referredto hereinafter, of the first gear mechanism GA1, a first clutch actuator51 (see FIG. 2), and a return spring (not shown) which urges the innerclutch plate 5 b such that the inner clutch plate 5 b is moved away fromthe outer clutch plate 5 a.

The first clutch actuator 51 uses oil pressure as a motive power source.When a drive signal is input from the ECU 2, the first clutch actuator51 drives the inner clutch plate 5 b toward the outer clutch plate 5 aagainst the urging force of the return spring. The first clutch actuator51 is thus driven by the ECU 2, whereby the degree of engagement of thefirst clutch 5 is changed to engage and disengage the first clutch 5,whereby the engine 3 and the first input shaft 11 are connected to anddisconnected from each other.

Further, the first clutch actuator 51 is provided with a first oilpressure sensor 61 (see FIG. 2). The first oil pressure sensor 61detects oil pressure supplied to the first clutch actuator 51(hereinafter referred to as the “first clutch oil pressure PO1”), anddelivers a signal indicative of the detected first clutch oil pressurePal to the ECU 2. The ECU 2 determines whether the first clutch 5 isengaged or disengaged, based on the detected first clutch oil pressurePO1. In this case, the degree of engagement of the first clutch 5becomes larger as the first clutch oil pressure PO1 is larger, and whenthe first clutch oil pressure PO1 is equal to a predetermineddisengagement pressure PREL, the first clutch 5 is in a disengagedstate.

The second clutch 6 is a wet multiple-disc clutch, similar to the firstclutch 5, and includes an outer clutch plate 6 a coaxially fixed to theouter clutch plate 5 a of the first clutch 5, an inner clutch plate 6 bcoaxially fixed to one end of a second input shaft 12, referred tohereinafter, of the second gear mechanism GA2, a second clutch actuator52 (see FIG. 2), and a return spring (not shown) which urges the innerclutch plate 6 b such that the inner clutch plate 6 b is moved away fromthe outer clutch plate 6 a.

The second clutch actuator 52 is configured similarly to theabove-described first clutch actuator 51. When a drive signal is inputfrom the ECU 2, the second clutch actuator 52 drives the inner clutchplate 6 b of the second clutch 6 toward the outer clutch plate 6 aagainst the urging force of the return spring. The second clutchactuator 52 is thus driven by the ECU 2, whereby the degree ofengagement of the second clutch 6 is changed to engage and disengage thesecond clutch 6, whereby the engine 3 and the second input shaft 12 areconnected to and disconnected from each other.

Further, the second clutch actuator 52 is provided with a second oilpressure sensor 62 (see FIG. 2). The second oil pressure sensor 62detects oil pressure supplied to the second clutch actuator 52(hereinafter referred to as the “second clutch oil pressure PO2”), anddelivers a signal indicative of the detected second clutch oil pressurePO2 to the ECU 2. The ECU 2 determines whether the second clutch 6 isengaged or disengaged, based on the detected second clutch oil pressurePO2. In this case, the degree of engagement of the second clutch 6becomes larger as the second clutch oil pressure PO2 is larger, and whenthe second clutch oil pressure PO2 is equal to the above-mentionedpredetermined disengagement pressure PREL, the second clutch 6 is in adisengaged state.

The first gear mechanism GA1 is used for transmitting input motive powerto the drive wheels DW in a state in which the speed of the motive poweris changed at a transmission gear ratio of one of first, third, fifth,and seventh speed positions for forward travel. These first to seventhspeed positions have their transmission gear ratios set to higher-speedvalues as the number of the speed position is larger. The same appliesto speed positions, referred to hereinafter, of the second gearmechanism GA2. Specifically, the first gear mechanism GA1 includes aplanetary gear unit 7, the first input shaft 11, a third speed drivegear 13, a fifth speed drive gear 14, and a seventh speed drive gear 15,which are arranged coaxially with the crankshaft 3 a of the engine 3, anoutput shaft 30 arranged in parallel with the first input shaft 11, asecond-third speed driven gear 31, a fourth-fifth speed driven gear 32,and a sixth-seventh speed driven gear 33.

The planetary gear unit 7 is of a single planetary type, and includes asun gear 7 a, a ring gear 7 b which is rotatably provided around anouter periphery of the sun gear 7 a, a plurality of planetary gears 7 c(only two of which are shown) in mesh with the gears 7 a and 7 b, and arotatable carrier 7 d rotatably supporting the planetary gears 7 c. Thesun gear 7 a is coaxially fixed to the above-mentioned output shaft 4 aof the motor 4, and is coaxially fixed to the other end of the firstinput shaft 11. The first input shaft 11 is rotatably supported by acasing 8 via bearings (not shown). With the above arrangement, the innerclutch plate 5 b of the first clutch 5, the first input shaft 11, thesun gear 7 a, and the output shaft 4 a of the motor 4 are rotatable inunison with each other. Further, the carrier 7 d is coaxially fixed to ahollow cylindrical rotating shaft 19 rotatably supported by bearings(not shown). The first input shaft 11 is relatively rotatably arrangedinside the rotating shaft 19. The rotating shaft 19 is rotatablysupported by the casing 8 via bearings (not shown).

The third speed drive gear 13 and the seventh speed drive gear 15 arecoaxially and relatively rotatably arranged on the first input shaft 11.The fifth speed drive gear 14 is coaxially fixed to the above-mentionedrotating shaft 19. With the above arrangement, the fifth speed drivegear 14, the rotating shaft 19, and the carrier 7 d are rotatable inunison with each other. Further, the third speed drive gear 13, theseventh speed drive gear 15, and the fifth speed drive gear 14 arearranged at respective locations in the mentioned order from the side ofthe engine 3 toward the side of the motor 4.

The second-third speed driven gear 31, the fourth-fifth speed drivengear 32, and the sixth-seventh speed driven gear 33 are coaxially fixedto the output shaft 30, and are in mesh with the third speed drive gear13, the fifth speed drive gear 14, and the seventh speed drive gear 15,respectively. The output shaft 30 is rotatably supported by the casing 8via bearings (not shown). Further, an output gear 34 is coaxially fixedto the output shaft 30. A gear of a final reduction gear box FG is inmesh with the output gear 34. The final reduction gear box FG isconnected to the above-mentioned pair of drive wheels DW via a pair ofdrive shafts DS (only one of which is shown).

Further, the above-mentioned second gear mechanism GA2 transmits inputmotive power to the drive wheels DW in a state in which the speed of themotive power is changed at a transmission gear ratio of one of second,fourth, and sixth speed positions for forward travel. In the automatictransmission 1, the second speed position is set as a speed position forstarting the vehicle V. Specifically, the second gear mechanism GA2includes the second input shaft 12 arranged coaxially with thecrankshaft 3 a, an auxiliary shaft 20 arranged in parallel with theabove-described first input shaft 11 and output shaft 30, a second speeddrive gear 21, a fourth speed drive gear 22, a sixth speed drive gear23, and the above-described output shaft 30, second-third speed drivengear 31, fourth-fifth speed driven gear 32, and sixth-seventh speeddriven gear 33. As described above, the output shaft 30, thesecond-third speed driven gear 31, the fourth-fifth speed driven gear32, and the sixth-seventh speed driven gear 33 are shared by the firstand second gear mechanisms GA1 and GA2.

The second input shaft 12 is formed to be hollow, and is rotatablysupported by the casing 8 via bearings (not shown). A gear 12 a iscoaxially fixed to the other end of the second input shaft 12 and is inmesh with an idler gear 44. The above-mentioned auxiliary shaft 20 isrotatably supported by the casing 8 via bearings (not shown). An inputgear 24 is coaxially fixed to the auxiliary shaft 20 and is in mesh withthe above-mentioned idler gear 44. Further, the second speed drive gear21, the fourth speed drive gear 22, and the sixth speed drive gear 23are coaxially and relatively rotatably arranged on the auxiliary shaft20, and are in mesh with the second-third speed driven gear 31, thefourth-fifth speed driven gear 32, and the sixth-seventh speed drivengear 33, respectively. The input gear 24, the second speed drive gear21, the sixth speed drive gear 23, and the fourth speed drive gear 22are arranged at respective locations in the mentioned order from theside of the engine 3 toward the side of the motor 4.

The reverse mechanism RA transmits the motive power of the engine 3 tothe drive wheels DW such that the drive wheels DW perform reverserotation in order to cause the vehicle V to travel backward, andincludes a reverse shaft 40, a reverse input gear 41, and a reverse gear42. The reverse input gear 41 is coaxially fixed to the reverse shaft 40and is in mesh with the above-mentioned idler gear 44. Further, thereverse gear 42 is coaxially and relatively rotatably arranged on thereverse shaft 40 and is in mesh with an input gear 11 a coaxially fixedto the first input shaft 11.

The above-mentioned connection/disconnection mechanism is provided forconnecting/disconnecting transmission of motive power from the first andsecond gear mechanisms GA1 and GA2 and the reverse mechanism. RA to thedrive wheels DW, and includes a third speed synchronization mechanism16, a fifth-seventh speed synchronization mechanism 17, a first speedsynchronization mechanism 18, a second speed synchronization mechanism25, a fourth-sixth speed synchronization mechanism 26, and a reversesynchronization mechanism 43. Although detailed description is omitted,the third speed synchronization mechanism 16 is configured similarly toa synchronization mechanism proposed by the present applicant e.g. inthe Publication of Japanese Patent No. 4242189, and is connected to agear actuator 53 (see FIG. 2) via a third speed shift fork (not shown).

The gear actuator 53 is a combination of an electric motor, a gearmechanism, and the like, and actuates the third speed synchronizationmechanism 16 via the third speed shift fork according to a drive signalfrom the ECU 2. This causes the third speed synchronization mechanism 16to selectively execute a third speed position in-gear operation forconnecting the third speed drive gear to the first input shaft 11, and adisconnection operation for disconnecting them from each other.

The fifth-seventh speed synchronization mechanism 17, the first speedsynchronization mechanism 18, the second speed synchronization mechanism25, the fourth-sixth speed synchronization mechanism 26, and the reversesynchronization mechanism 43 are all configured similarly to theabove-mentioned third speed synchronization mechanism 16, and areconnected to the gear actuator 53 via a fifth-seventh speed shift fork,a first speed shift fork, a second speed shift fork, a fourth-sixthspeed shift fork, and a reverse shift fork, respectively. Thefifth-seventh speed synchronization mechanism 17 is actuated by the gearactuator 53, to thereby selectively execute a fifth speed positionin-gear operation for connecting the fifth speed drive gear 14 to thefirst input shaft 11, a seventh speed position in-gear operation forconnecting the seventh speed drive gear 15 to the first input shaft 11,and a disconnection operation for disconnecting both the fifth andseventh speed drive gears 14 and 15 from the first input shaft 11. Thefirst speed synchronization mechanism 18 is actuated by the gearactuator 53, to thereby selectively execute a first speed positionin-gear operation for connecting the ring gear 7 b of the planetary gearunit 7 to the casing 8, and a disconnection operation for disconnectingthem from each other.

Further, the second speed synchronization mechanism 25 is actuated bythe gear actuator 53, to thereby selectively execute a second speedposition in-gear operation for connecting the second speed drive gear 21to the auxiliary shaft 20, and a disconnection operation fordisconnecting them from each other. Further, the fourth-sixth speedsynchronization mechanism 26 is actuated by the gear actuator 53, tothereby selectively execute a fourth speed position in-gear operationfor connecting the fourth speed drive gear 22 to the auxiliary shaft 20,a sixth speed position in-gear operation for connecting the sixth speeddrive gear 23 to the auxiliary shaft 20, and a disconnection operationfor disconnecting both the fourth and sixth speed drive gears 22 and 23from the auxiliary shaft 20. The reverse synchronization mechanism 43 isactuated by the gear actuator 53, to thereby selectively execute abackward travel position in-gear operation for connecting the reversegear 42 to the reverse shaft 40, and a disconnection operation fordisconnecting them from each other.

In the automatic transmission 1 configured as above, the motive power ofthe engine 3 is transmitted to the drive wheels DW by the first orsecond gear mechanism GA1 or GA2 in a state in which the speed of themotive power is stepwise changed. Specifically, when the first gearmechanism GA1 is used, the first clutch 5 is engaged to thereby connectbetween the crankshaft 3 a and the first input shaft 11, and the secondclutch 6 is disengaged to thereby disconnect between the crankshaft 3 aand the second input shaft 12. This causes the motive power of theengine 3 to be transmitted to the first input shaft 11.

In this case, when the speed of the motive power of the engine 3 ischanged at a transmission gear ratio of the first speed position of thefirst gear mechanism GA1, the ring gear 7 b is connected to the casing 8by the above-mentioned first speed position in-gear operation of thefirst speed synchronization mechanism 18, whereby the ring gear 7 b ismade unrotatable. Further, the third, fifth, and seventh speed drivegears 13, 14, and 15 are disconnected from the first input shaft 11 bythe disconnection operations of the third speed synchronizationmechanism 16 and the fifth-seventh speed synchronization mechanism 17.From the above, the speed position of the first gear mechanism GA1 isset to the first speed position, and the motive power transmitted fromthe engine 3 to the first input shaft 11 is transmitted to the right andleft drive wheels DW via the sun gear 7 a and the carrier 7 d of theplanetary gear unit 7, the rotating shaft 19, the fifth speed drive gear14, the fourth-fifth speed driven gear 32, the output shaft 30, theoutput gear 34, the final reduction gear box FG, and the right and leftdrive shafts DS. At this time, the speed of the motive power of theengine 3 is changed at the transmission gear ratio of the first speedposition determined by the number of gear teeth of the sun gear 7 a, thenumber of gear teeth of the ring gear 7 b, the number of gear teeth ofthe fifth speed drive gear 14, the number of gear teeth of thefourth-fifth speed driven gear 32, and so forth.

Further, when the speed of the motive power of the engine 3 is changedat a transmission gear ratio of the third speed position of the firstgear mechanism GA1, the ring gear 7 b is disconnected from the casing 8by the disconnection operation of the first speed synchronizationmechanism 18, whereby the rotation of the ring gear 7 b is permitted.Further, the third speed drive gear 13 is connected to the first inputshaft 11 by the third speed position in-gear operation of the thirdspeed synchronization mechanism 16, while both the fifth and seventhspeed drive gears 14 and 15 are disconnected from the first input shaft11 by the disconnection operation of the fifth-seventh speedsynchronization mechanism 17. From the above, the speed position of thefirst gear mechanism GA1 is set to the third speed position, and themotive power transmitted from the engine 3 to the first input shaft 11is transmitted to the right and left drive wheels DW via the third speeddrive gear 13, the second-third speed driven gear 31, the output shaft30, and so forth. At this time, the speed of the motive power of theengine 3 is changed at the transmission gear ratio of the third speedposition determined e.g. by the number of gear teeth of the third speeddrive gear 13, and the number of gear teeth of the second-third speeddriven gear 31.

Note that cases where the speed of the motive power of the engine 3 ischanged at respective transmission gear ratios of the fifth and seventhspeed positions of the first gear mechanism GA1 are distinguished fromthe above-described case of the third speed position only in that thefifth speed drive gear 14 and the seventh speed drive gear 15 areconnected to the first input shaft 11, respectively, and the otheroperations are basically the same as in the case of the third speedposition. Therefore, detailed description of the respective cases of thefifth and seventh speed positions will be omitted.

Further, the disconnection operations are executed by the third speedsynchronization mechanism 16, the fifth-seventh speed synchronizationmechanism 17, and the first speed synchronization mechanism 18, wherebythe third, fifth, and seventh speed drive gears 13, 14, and 15 aredisconnected from the first input shaft 11, and the ring gear 7 b isdisconnected from the casing 8. This disconnects transmission of themotive power from the first gear mechanism GA1 to the drive wheels DW.Hereinafter, to execute the disconnection operations by the third speedsynchronization mechanism 16, the fifth-seventh speed synchronizationmechanism 17, and the first speed synchronization mechanism 18 will bereferred to as “to execute a first disconnection operation”, and a statein which transmission of the motive power from the first gear mechanismGA1 to the drive wheels DW is disconnected by executing the firstdisconnection operation is referred to as the “neutral state of thefirst gear mechanism GA1” as deemed appropriate.

Furthermore, when the motive power of the engine 3 is transmitted to thedrive wheels DW using the second gear mechanism GA2, the first clutch 5is disengaged to thereby disconnect between the crankshaft 3 a and thefirst input shaft 11, and the second clutch 6 is engaged to therebyconnect between the crankshaft 3 a and the second input shaft 12. Thiscauses the motive power of the engine 3 to be transmitted to the secondinput shaft 12.

In this case, when the speed of the motive power of the engine 3 ischanged at a transmission gear ratio of the second speed position of thesecond gear mechanism GA2, the second speed drive gear 21 is connectedto the auxiliary shaft 20 by the second speed position in-gear operationof the second speed synchronization mechanism 25, and both the fourthand sixth speed drive gears 22 and 23 are disconnected from theauxiliary shaft 20 by the disconnection operation of the fourth-sixthspeed synchronization mechanism 26. From the above, the speed positionof the second gear mechanism GA2 is set to the second speed position,and the motive power transmitted from the engine 3 to the second inputshaft 12 is transmitted to the drive wheels DW via the gear 12 a, theidler gear 44, the input gear 24, the auxiliary shaft 20, the secondspeed drive gear 21, the second-third speed driven gear 31, the outputshaft 30, and so forth. At this time, the speed of the motive power ofthe engine 3 is changed at the transmission gear ratio of the secondspeed position determined by the number of gear teeth of the secondspeed drive gear 21, the number of gear teeth of the second-third speeddriven gear 31, and so forth.

Note that cases where the speed of the motive power of the engine 3 ischanged at respective transmission gear ratios of the fourth and sixthspeed position are distinguished from the above-described case of thesecond speed position only in that the fourth and sixth speed drivegears 22 and 23 are connected to the auxiliary shaft 20, respectively,and the other operations are basically the same as in the case of thesecond speed position. Therefore, detailed description of the respectivecases of the fourth and sixth speed positions will be omitted.

Further, the second, fourth, and sixth speed drive gears 21, 22, and 23are disconnected from the auxiliary shaft 20 by executing thedisconnection operations by the second speed synchronization mechanism25 and the fourth-sixth speed synchronization mechanism 26, wherebytransmission of the motive power from the second gear mechanism GA2 tothe drive wheels DW is disconnected. Hereafter, to execute thedisconnection operations by the second speed synchronization mechanism25 and the fourth-sixth speed synchronization mechanism 26 will bereferred to as “to execute a second disconnection operation”, and astate in which transmission of the motive power from the second gearmechanism GA2 to the drive wheels DW is disconnected by executing thesecond disconnection operation is referred to as the “neutral state ofthe second gear mechanism GA2” as deemed appropriate.

Furthermore, when the motive power transmitted to the first or secondinput shaft 11 or 12 is transmitted to the drive wheels DW by changingthe direction of rotation of the motive power to the direction ofreverse rotation using the reverse mechanism RA, the first and secondgear mechanisms GA1 and GA2 are controlled to the neutral states byexecuting the above-described first and second disconnection operations,and the reverse gear 42 is connected to the reverse shaft 40 by theabove-described backward travel position in-gear operation of thereverse synchronization mechanism 43. From the above, the motive powertransmitted to the first or second input shaft 11 or 12 is transmittedto the drive wheels DW via the reverse mechanism RA and so forth in astate in which the direction of rotation of the motive power is changedto the direction of reverse rotation.

Further, the reverse gear 42 is disconnected from the reverse shaft 40by executing the disconnection operation by the reverse synchronizationmechanism 43, whereby transmission of motive power from the reversemechanism RA to the drive wheels DW is disconnected. Hereinafter, toexecute the disconnection operation by the reverse synchronizationmechanism 43 will be referred to as “to execute a third disconnectionoperation”, and a state in which transmission of the motive power fromthe reverse mechanism RA to the drive wheels DW is disconnected byexecuting the third disconnection operation is referred to as the“neutral state of the reverse mechanism RA” as deemed appropriate.

A speed position sensor 63 (see FIG. 2) is disposed close to the gearactuator 53. The speed position sensor 63 detects an operating state ofthe gear actuator 53, and delivers a signal indicative of the detectedoperating state of the gear actuator 53 to the ECU 2. The ECU 2determines whether or not each of the above-described first to seventhspeed position in-gear operations and backward travel position in-gearoperation has been completed, based on the detection signal from thespeed position sensor 63.

Further, as shown in FIG. 3, the automatic transmission 1 is providedwith a lubricating oil supply system 80. The lubricating oil supplysystem 80 supplies lubricating oil to the motor 4, the first and secondclutches 5 and 6, and so forth, and includes an oil pump 81, a reliefvalve 82, an oil pan 83, a flow rate control valve 84, and a flowrate-switching valve 85.

The oil pump 81 is of a mechanically-driven type using the engine 3 as amotive power source. During operation of the oil pump 81, the oil pump81 draws lubricating oil stored in the oil pan 83 via an oil passage 86a, and discharges the drawn lubricating oil into the relief valve 82 andthe flow rate control valve 84 via an oil passage 86 b and an oilpassage 86 c. In this case, when a discharge pressure from the oil pump81 is not lower than a predetermined relief pressure, the relief valve82 is opened, whereby the lubricating oil is returned to the oil passage86 a via an oil passage 86 e. Further, when the discharge pressure fromthe oil pump 81 is lower than the predetermined relief pressure, therelief valve 82 is held in a closed state, whereby the lubricating oildischarged from the oil pump 81 is supplied to the flow rate-switchingvalve 85 via an oil passage 86 d.

Further, the flow rate control valve 84 is of a normally closed type,and is electrically connected to the ECU 2. When a drive signal is beinginput from the ECU 2, the flow rate control valve 84 is held in an openstate, whereby a control oil pressure is supplied to the flowrate-switching valve 85 via an oil passage 86 f. On the other hand, whenthe drive signal is not being input from the ECU 2, the flow ratecontrol valve 84 is held in a closed state, whereby the control oilpressure is not supplied to the flow rate-switching valve 85.

Further, the flow rate-switching valve 85 is a spool valve, and supplieslubricating oil supplied from the oil pump 81 to the motor 4 and thefirst and second clutches 5 and 6 by distributing the lubricating oiltherebetween via oil passages 86 g and 86 h, respectively, while havinga distribution ratio for distributing the lubricating oil between thetwo switched according to whether or not the control oil pressure issupplied from the flow rate control valve 84. Specifically, when thecontrol oil pressure is supplied from the flow rate control valve 84 tothe flow rate-switching valve 85, the lubricating oil is supplied to thefirst and second clutches 5 and 6 at a large flow rate, but is suppliedto the motor 4 at a small flow rate. Further, when the control oilpressure is not supplied from the flow rate control valve 84 to the flowrate-switching valve 85, inversely to the above, the lubricating oil issupplied to the first and second clutches 5 and 6 at a small flow rate,but is supplied to the motor 4 at a large flow rate. Hereinafter, theamount of the lubricating oil supplied to the first and second clutches5 and 6 is referred to as the “clutch lubricating oil supply amount”.

Further, the vehicle V is equipped with a shift lever device (notshown), an accelerator pedal (not shown), a brake pedal (not shown), anda vehicle speed sensor 64. The shift lever device is a floor shiftlever, and is provided with five positions, i.e. a parking position P, areverse position R, a neutral position N, a drive position D, and asport position S, as shift positions. The parking position P and theneutral position N correspond to non-traveling positions for stoppage ofthe vehicle V. The drive position D and the sport position S correspondto forward travel positions for forward travel of the vehicle V, and thereverse position R corresponds to a backward travel position forbackward travel of the vehicle V. The shift position of the shift leverdevice is selectively switched to one of the above five positionsaccording to a shift operation by a driver. Note that the presentinvention can be applied to a vehicle of a type which is not equippedwith the sport position S of the above-described five positions.Further, the vehicle speed sensor 64 detects a vehicle speed VP of thevehicle V, and delivers a signal indicative of the detected vehiclespeed VP to the ECU 2.

Furthermore, the shift lever device, the accelerator pedal, and thebrake pedal are provided with a shift position sensor 65, an acceleratorpedal opening sensor 66, and a brake switch 67 (see FIG. 2),respectively. The shift position sensor 65 detects the shift position SPof the shift lever device, and delivers a signal indicative of thedetected shift position SP to the ECU 2. The accelerator pedal openingsensor 66 detects a degree of opening AP of the accelerator pedal(hereafter referred to as the “accelerator pedal opening AP”), which isan operation amount of the accelerator pedal, and delivers a signalindicative of the detected accelerator pedal opening AP to the ECU 2.When the brake pedal is stepped on, the brake switch 67 delivers an onsignal to the ECU 2, and otherwise it delivers an off signal to the ECU2.

The ECU 2 is implemented by a microcomputer comprised of a CPU, a RAM, aROM, and an I/O interface (none of which are shown), and executesprocesses shown in FIGS. 4 to 6 based on the detection signals from theaforementioned sensors 61 to 66 and the output signals from the brakeswitch 67, according to control programs stored in the ROM.

FIG. 4 shows an in-gear control process for controlling operations ofthe connection/disconnection mechanism including the above-describedfirst speed synchronization mechanism 18. This process is repeatedlyexecuted whenever a predetermined time period (e.g. 100 msec) elapses,during stoppage of and at the standing start of the vehicle V. First, ina step 1 (shown as S1 in abbreviated form; the following steps are alsoshown in abbreviated form), it is determined whether or not astoppage/standing start time flag F_STPORDR is equal to 1. Thisstoppage/standing start time flag F_STPORDR is set to 1 during stoppageof or at the standing start of the vehicle V, and is set based on thedetected vehicle speed VP, the accelerator pedal opening AP, and theoutput signal from the brake switch 67.

If the answer to the question of the step 1 is negative (NO)(F_STPORDR=0), the present process is immediately terminated, whereas ifthe answer to the question of the step 1 is affirmative (YES), i.e. ifthe vehicle V is at a stop or at a standing start, it is determinedwhether the detected shift position SP is at the parking position P orthe neutral position N (step 2). If the answer to this question isaffirmative (YES), i.e. if the shift position SP is at the parkingposition P or the neutral position N, first neutral control is executed(step 3). In the first neutral control, the connection/disconnectionmechanism is controlled, whereby the above-described first to thirddisconnection operations are executed. With these operations, the firstand second gear mechanisms GA1 and GA2, and the reverse mechanism RAenter the above-described neutral states, whereby transmission of themotive power from the first and second gear mechanisms GA1 and GA2, andthe reverse mechanism RA to the drive wheels DW is disconnected.

In a step 4 following the above-described step 3, a second in-gearcompletion flag F_FIN2 and a first in-gear completion flag F_FIN1, whichare referred to hereinafter, are set to 0. Then, a clutch engagementpermission flag F_ALLO, referred to hereinafter, is set to 0 (step 5),followed by terminating the present process.

On the other hand, if the answer to the question of the above-describedstep 2 is negative (NO), i.e. if the detected shift position SP is notat either of the parking position P and the neutral position N, it isdetermined whether the shift position SP is at the drive position D orthe sport position S (step 6). If the answer to this question isnegative (NO), i.e. if the shift position SP is not at any of theparking position P, the neutral position N, the drive position D, andthe sport position S but is at the reverse position R, the presentprocess is immediately terminated.

On the other hand, if the answer to the question of the above-describedstep 6 is affirmative (YES), i.e. if the shift position SP is at thedrive position D or the sport position S, a second neutral control isexecuted (step 7). In the second neutral control, theconnection/disconnection mechanism is controlled, whereby the thirddisconnection operation is executed. With this operation the reversemechanism RA enters the neutral state, whereby transmission of themotive power from the reverse mechanism RA to the drive wheels DW isdisconnected.

In a step 8 following the above-described step 7, it is determinedwhether or not the second in-gear completion flag F_FIN2 is equal to 1.If the answer to this question is negative (NO) (F_FIN2=0), the secondspeed position in-gear operation is executed (step 9). With thisoperation, the speed position of the second gear mechanism GA2 is set tothe second speed position.

Next, it is determined whether or not the second speed position in-gearoperation has been completed (step 10). This determination is performedbased on the detection signal from the above-described speed positionsensor 63. If the answer to the question of the step 10 is negative(NO), i.e. if the second speed position in-gear operation has not beencompleted, the present process is immediately terminated, whereas if theanswer to the question of the step 10 is affirmative (YES), i.e. if thesecond speed position in-gear operation has been completed, to indicatethe fact, the second in-gear completion flag F_FIN2 is set to 1 (step11), and the process proceeds to a step 12 following the step 11. Byexecuting the step 11, the answer to the question of the above-describedstep 8 becomes affirmative (YES), and in this case, the above-describedsteps 9 to 11 are skipped for the process to directly proceed to thestep 12.

In the step 12 et seq., execution of the first speed position in-gearoperation and setting of the first in-gear completion flag F_FIN1 areperformed, similarly to the steps 8 to 11. Specifically, in the step 12,it is determined whether or not the first in-gear completion flag F_FIN1is equal to 1. If the answer to this question is negative (NO)(F_FIN1=0), the first speed position in-gear operation is executed (step13). With this operation, the speed position of the first gear mechanismGA1 is set to the first speed position.

Next, it is determined whether or not the first speed position in-gearoperation has been completed (step 14). This determination is performedbased on the detection signal from the above-described speed positionsensor 63. If the answer to the question of the step 14 is negative(NO), i.e. if the first speed position in-gear operation has not beencompleted, the present process is immediately terminated, whereas if theanswer to the question of the step 14 is affirmative (YES), i.e. if thefirst speed position in-gear operation has been completed, to indicatethe fact, the first in-gear completion flag F_FIN1 is set to 1 (step15), followed by terminating the present process. By executing the step15, the answer to the question of the above-described step 12 becomesaffirmative (YES), and in this case, the above-described steps 13 to 15are skipped for the present process to be immediately terminated.

As described hereinabove, according to the above-described in-gearcontrol process, during stoppage of and at the standing start of thevehicle V (YES to the step 1), when the shift position SP is at theparking position P or the neutral position N (YES to the step 2), thefirst neutral control is executed (the step 3). With this operation, thefirst to third disconnection operations of the connection/disconnectionmechanism are executed, whereby transmission of the motive power fromthe first and second gear mechanisms GA1 and GA2, and the reversemechanism RA to the drive wheels DW is interrupted.

From this state, when the shift position SP is switched to the driveposition D or the sport position S (YES to the step 6), the secondneutral control, the second speed position in-gear operation, and thefirst speed position in-gear operation are executed (the steps 7, 9, and13). With these operations, transmission of the motive power from thereverse mechanism RA to the drive wheels DW continues to bedisconnected, and the speed positions of the first and second gearmechanisms GA1 and GA2 are set to the first speed position and thesecond speed position, respectively. Then, there is connectedtransmission of the motive power from the first and second gearmechanisms GA1 and GA2 to the drive wheels DW by the speed positions.Further, when the second and first speed position in-gear operationshave been completed, to indicate the fact, the second and first in-gearcompletion flags F_FIN2 and F_FIN1 are set to 1, respectively (the steps11 and 15).

Note that as shown in FIG. 4, the first speed position in-gear operationis executed after the completion of the second speed position in-gearoperation because the second and first speed position in-gear operationsare executed by the same gear actuator 53, and the second speed positionof the second gear mechanism GA2 is set as the speed position for thestanding start of the vehicle V, as mentioned above.

Next, a clutch control process for controlling the operations of thefirst and second clutches 5 and 6 during stoppage of and at the standingstart of the vehicle V will be described with reference to FIG. 5.First, in a step 21 in FIG. 5, it is determined whether or not theabove-mentioned stoppage/standing start time flag F_STPORDR is equalto 1. If the answer to this question is negative (NO), the presentprocess is immediately terminated, whereas if the answer to the questionis affirmative (YES), i.e. if the vehicle V is at a stop or at astanding start, it is determined whether the detected shift position SPis at the parking position P or the neutral position N (step 22).

If the answer to the question of the step 22 is affirmative (YES), i.e.if the shift position SP is at the parking position P or the neutralposition N, clutch disengagement control is executed (step 23), followedby terminating the present process. By executing the step 23, the firstand second clutches 5 and 6 are controlled to the respective disengagedstates, whereby the first and second clutch oil pressures PO1 and PO2become equal to the above-mentioned disengagement pressure PREL.

On the other hand, if the answer to the question of the step 22 isnegative (NO), i.e. if the shift position SP is not at either theparking position P or the neutral position N, it is determined whetheror not the shift position SP is at the drive position D or the sportposition S (step 24). If the answer to this question is negative (NO),i.e. if the shift position SP is not at any of the parking position P,the neutral position N, the drive position D, and the sport position S,but is at the reverse position R, the present process is immediatelyterminated.

On the other hand, if the answer to the question of the above-describedstep 24 is affirmative (YES), i.e. if the shift position SP is at thedrive position D or the sport position S, it is determined whether ornot the clutch engagement permission flag F_ALLO is equal to 1 (step25). If the answer to this question is negative (NO) (F_ALLO=0), it isdetermined whether or not the second in-gear completion flag F_FIN2 setin the above-described step 4 or 11 in FIG. 4 is equal to 1 (step 26).If the answer to this question is negative (NO) (F_FIN2=0), i.e. if thesecond speed position in-gear operation has not been completed, theclutch disengagement control is executed by executing theabove-described step 23, followed by terminating the present process.

On the other hand, if the answer to the question of the above-describedstep 26 is affirmative (YES) (F_FIN2=1), i.e. if the second speedposition in-gear operation has been completed, it is determined whetheror not the first in-gear completion flag F_FIN1 is equal to 1 (step 27).If the answer to this question is negative (NO) (F_FIN1=0), i.e. if thefirst speed position in-gear operation has not been completed, it isdetermined whether or not a standing start request flag F_REQDR is equalto 1 (step 28). This standing start request flag F_REQDR is set to 1when it is determined that a request for the standing start of thevehicle V has been made by the driver. In this case, it is determinedthat a request for the standing start of the vehicle V has been made bythe driver when the following conditions (a) and (b) are both satisfied.

(a) The brake pedal is not stepped on, whereby the brake switch 67delivers the off signal to the ECU 2.

(b) The accelerator pedal is stepped on, whereby the detectedaccelerator pedal opening AP is larger than 0.

If the answer to the question of the step 28 is negative (NO)(F_REQDR=0), i.e. if the request for the standing start of the vehicle Vhas not been made by the driver, the clutch disengagement control isexecuted by executing the above-described step 23, followed byterminating the present process. On the other hand, if the answer to thequestion of the step 28 is affirmative (YES) (F_REQDR=1), i.e. if therequest for the standing start of the vehicle V has been made by thedriver, second standing-start clutch control is executed (step 29),followed by terminating the present process. In this secondstanding-start clutch control, by progressively increasing the degree ofengagement of the second clutch 6, the second clutch 6 is completelyengaged, and the first clutch 5 is held in the disengaged state.

On the other hand, if the answer to the question of the step 27 isaffirmative (YES) (F_FIN1=1), i.e. if the second and first speedposition in-gear operations have been completed, to permit engagement ofthe first and second clutches 5 and 6, the clutch engagement permissionflag F_ALLO is set to 1 (step 30), and the process proceeds to a step 31following the step 30. By executing the step 30, the answer to thequestion of the above-described step becomes affirmative (YES). In thiscase, the above-described steps 26, 27, and 30 are skipped for thepresent process to directly proceed to the step 31.

In the step 31, it is determined whether or not the above-mentionedstanding start request flag F_REQDR is equal to 1. If the answer to thisquestion is negative (NO) (F_REQDR=0), i.e. if the request for thestanding start of the vehicle V has not been made by the driver, theclutch disengagement control is executed (step 32), similarly to theabove-described step 23, followed by terminating the present process.

On the other hand, if the answer to the question of the above-describedstep 31 is affirmative (YES) (F_REQDR=1), i.e. if the request for thestanding start of the vehicle V has been made by the driver, it isdetermined whether or not a required torque TREQ is larger than apredetermined value TREF (step 33). This required torque TREQ is torquerequired for the drive wheels DW, and is calculated by searching apredetermined map according to the accelerator pedal opening AP. If theanswer to the question of the step 33 is negative (NO), i.e. if therequired torque TREQ is not larger than the predetermined value TREF,the second standing-start clutch control is executed by executing theabove-described step 29, followed by terminating the present process.

On the other hand, if the answer to the question of the above-describedstep 33 is affirmative (YES), i.e. if the required torque TREQ is largerthan the predetermined value TREF, first standing-start clutch controlis executed (step 34), followed by terminating the present process. Inthis first standing-start clutch control, by progressively increasingthe degree of engagement of the first clutch 5, the first clutch 5 iscompletely engaged, and the second clutch 6 is held in the disengagedstate.

As described hereinabove, according to the above-described clutchcontrol process, during stoppage of and at the standing start of thevehicle V (YES to the step 21), when the shift position SP is at theparking position P or the neutral position N (YES to the step 2), theclutch disengagement control is executed (the step 23), whereby thefirst and second clutches 5 and 6 are both controlled to the disengagedstates.

From this state, when the shift position SP is switched to the driveposition D or the sport position S (YES to the step 24), if the secondspeed position in-gear operation has not been completed (NO to the step26), the clutch disengagement control is executed (the step 23), wherebythe first and second clutches 5 and 6 continue to be held in thedisengaged states. In this case, also when the second speed positionin-gear operation has been completed but the first speed positionin-gear operation has not been completed (YES to the step 26, and NO tothe step 27), and also the request for the standing start of the vehicleV has not been made by the driver (NO to the step 28), the clutchdisengagement control is executed. On the other hand, when the requestfor the standing start of the vehicle V has been made by the driver (YESto the step 28), the second standing-start clutch control is executed(the step 29). With this operation, the degree of engagement of only thesecond clutch 6 is progressively increased, whereby only the secondclutch 6 is completely engaged.

Further, when the shift position SP is switched to the drive position Dor the sport position S, if both the first and second speed positionin-gear operations have been completed (YES to the step 26, and YES tothe step 27), the clutch engagement permission flag F_ALLO is set to 1(the step 30), whereby the engagement of the first and second clutches 5and 6 is permitted. In this case, if the request for the standing startof the vehicle V has not been made by the driver (NO to the step 31),the clutch disengagement control is executed (the step 32). With thisoperation, the first and second clutches 5 and 6 are held in thedisengaged states. Further, when the shift position SP is switched tothe drive position D or the sport position S, if both the first andsecond speed position in-gear operations have been completed, and alsothe request for the standing start of the vehicle V has been made by thedriver (YES to the step 31), the first or second standing-start clutchcontrol is executed based on a result of comparison between the requiredtorque TREQ and the predetermined value TREF (the steps 33, 34, and 29).

Next, a lubricating oil control process for controlling theabove-mentioned clutch lubricating oil supply amount (the amount oflubricating oil supplied to the first and second clutches 5 and 6) willbe described with reference to FIG. 6. This process is repeatedlyexecuted whenever a predetermined time period (e.g. 100 msec) elapses.First, in a step 41 shown in FIG. 6, it is determined whether or not thedetected first clutch oil pressure PO1 or second clutch oil pressure PO2is higher than the disengagement pressure PREL. If the answer to thisquestion is affirmative (YES), i.e. if the first or second clutch oilpressure PO1 or PO2 is higher than the disengagement pressure PREL, thatis, if the first or second clutch 5 or 6 is engaged, a targetlubricating oil supply amount QLOBJ is set to a first predeterminedamount QREF1 (step 42), followed by terminating the present process.This target lubricating oil supply amount QLOBJ is a target value of theclutch lubricating oil supply amount, and the above-mentioned flowrate-switching valve 85 is controlled such that the clutch lubricatingoil supply amount becomes equal to the target lubricating oil supplyamount QLOBJ.

On the other hand, if the answer to the question of the above-describedstep 41 is negative (NO), i.e. if both the first and second clutch oilpressures PO1 and PO2 are not higher than the disengagement pressurePREL, that is, if both the first and second clutches 5 and 6 aredisengaged, the target lubricating oil supply amount QLOBJ is set to asecond predetermined amount QREF2 (step 43), followed by terminating thepresent process. This second predetermined amount QREF2 is set to avalue smaller than the above-mentioned first predetermined amount QREF1.

Further, FIG. 7 shows an example of operation performed by the automatictransmission 1 when the request for the standing start of the vehicle Vhas not been made by the driver (F_REQDR=0). As shown in FIG. 7, whenthe shift position SP is at the parking position P (time t0 andthereafter), the first and second gear mechanisms GA1 and GA2 arecontrolled to the neutral states (the step 3 in FIG. 4); the first andsecond in-gear completion flags F_FIN1 and F_FIN2 and the clutchengagement permission flag F_ALLO are set to 0 (the steps 4 and 5); andthe first and second clutches 5 and 6 are controlled to the disengagedstates (the step 23 in FIG. 5). Along therewith, the first and secondclutch oil pressures PO1 and PO2 are held in the disengagement pressurePREL. Further, since the first and second clutch oil pressures PO1 andPO2 are equal to the disengagement pressure PREL, the target lubricatingoil supply amount QLOBJ is held at the second predetermined amount QREF2(the step 43 in FIG. 6)

Then, when the shift position SP is switched from the parking position Pto the drive position D (time t1), the first and second speed positionin-gear operations are executed (the steps 9 and 13 in FIG. 4). Alongwith the completion of this second speed position in-gear operation, thesecond in-gear completion flag F_FIN2 is set to 1 (time t2; the step11), and along with the completion of the first speed position in-gearoperation, the first in-gear completion flag F_FIN1 is set to 1 (timet3; the step 15). In this case, as described in the in-gear controlprocess (FIG. 4), the first and second speed position in-gear operationsare executed by the same gear actuator 53, and after the completion ofthe second speed position in-gear operation, the first speed positionin-gear operation is executed, whereafter this operation is completed,so that as shown in FIG. 7, the first in-gear completion flag F_FIN1 isset to 1 with some delay after the second in-gear completion flag F_FIN2has been set to 1.

Further, when not only the second speed position in-gear operation butalso the first speed position in-gear operation has been completed (timet3; YES to the step 27 in FIG. 5), the clutch engagement permission flagF_ALLO is set to 1 in order to permit the engagement of the first andsecond clutches 5 and 6 (step 30). In this case, since the request forthe standing start of the vehicle V has not been made by the driver (NOto the step 31), the clutch disengagement control is executed (the step32). With this operation, the first and second clutches 5 and 6 are heldin the disengaged states. Further, along with the above-mentionedcontrol of the first and second clutches 5 and 6, the first and secondclutch oil pressures PO1 and PO2 continue to be held at thedisengagement pressure PREL, and the target lubricating oil supplyamount QLOBJ continues to be held at the second predetermined amountQREF2.

FIG. 8 is a timing diagram showing a comparative example of theoperation shown in FIG. 7. As shown in FIG. 8, in this comparativeexample, after switching the shift position SP to the drive position D(time t4), when the second speed position in-gear operation has beencompleted (time t5), predetermined clutch control for creeping isexecuted. With this operation, the second clutch 6 is controlled to ahalf-clutch state, and the first clutch 5 is disengaged. Alongtherewith, the second clutch oil pressure PO2 is progressively increasedfrom the disengagement pressure PREL to a predetermined pressure PREF,and the first clutch oil pressure PO1 is held at the disengagementpressure PREL.

Further, to suit the progressive increase in the second clutch oilpressure PO2, the target lubricating oil supply amount QLOBJ is set tothe first predetermined amount QREF1 larger than the secondpredetermined amount QREF2. This controls the clutch lubricating oilsupply amount (the amount of lubricating oil supplied to the first andsecond clutches 5 and 6) such that the clutch lubricating oil supplyamount becomes equal to the first predetermined amount QREF1, wherebythe clutch friction of the first clutch 5 is increased, which in turnincreases motive power transmitted from the engine 3 to the first gearmechanism GA1 via the first clutch 5. As a consequence, the first inputshaft 11 of the first gear mechanism GA1 connected to the engine 3 isrotated, whereby a large differential rotation is generated between thefirst input shaft 11 and the carrier 7 connected to the drive wheels DWat rest, and accordingly a large differential rotation is generatedbetween the ring gear 7 b and the casing 8.

After that, the first speed position in-gear operation is completed, andthe first in-gear completion flag F_FIN1 is set to 1 (time t6). Asdescribed above, in the comparative example shown in FIG. 8, the secondclutch 6 is controlled to the half-clutch state before completion of thefirst speed position in-gear operation. This causes the ring gear 7 band the casing 8 to be connected in a state in which the largedifferential rotation is generated between the ring gear 7 b and thecasing 8, as mentioned above, and then the first speed position in-gearoperation is completed, which causes large vibration.

On the other hand, as described hereinabove with reference to FIGS. 5and 7, according to the automatic transmission 1 of the presentembodiment, the engagement of the first and second clutches 5 and 6 ispermitted only upon completion of both the second and first speedposition in-gear operations but is inhibited before completion of thesame, which prevents generation of large vibration, differently from theabove-described comparative example.

Further, FIG. 9 shows an example of operation performed by the automatictransmission 1 when the request for the standing start of the vehicle Vhas been made by the driver (F_REQDR=1). More specifically, FIG. 9 showsan example of operation of the automatic transmission 1 performed whenthe request for the standing start of the vehicle V is made after theshift position SP has been switched from the parking position P to thedrive position D and the second speed position in-gear operation hasbeen completed, before the first speed position in-gear operation iscompleted. In the example illustrated in FIG. 9, operations performedbefore the request for the standing start of the vehicle V is made(operations performed from time t7 to time immediately before time t10)are the same as the operations in the above-described example shown inFIG. 7, and hence operations performed after the request has been madewill be described, hereinafter.

In the case where the shift position SP has been switched from theparking position P to the drive position D, and the second speedposition in-gear operation has been completed, but the first speedposition in-gear operation has not been completed (NO to the step 27 inFIG. 5), when the request for the standing start of the vehicle V ismade (time t10, YES to the step 28), the second standing-start clutchcontrol is executed (the step 29). With this operation, the degree ofengagement of the second clutch 6 is progressively increased, wherebythe second clutch 6 is completely engaged, and the first clutch 5 iscontrolled to the disengaged state. From the above, the motive power ofthe engine 3 is transmitted to the second gear mechanism GA2 via thesecond clutch 6, and is transmitted to the drive wheels DW in a statechanged in speed at the transmission gear ratio of the second speedposition. Further, along with the above-described control of the firstand second clutches 5 and 6, the second clutch oil pressure PO2 isprogressively increased beyond the predetermined pressure PREF, and thefirst clutch oil pressure PO1 continues to be held at the disengagementpressure PREL. Further, to suit the increase of the second clutch oilpressure PO2 beyond the disengagement pressure PREL, the targetlubricating oil supply amount QLOBJ is set to the first predeterminedamount QREF1, similarly to the example shown in FIG. 7.

In this case, the second clutch 6 is engaged after completion of thesecond speed position in-gear operation, and before completion of thefirst speed position in-gear operation, so that although vibration iscaused by the engagement of the second clutch 6, the vehicle V isstarted, which makes it possible to prevent the driver from feelinguncomfortable to thereby prevent marketability from being degraded.

Further, FIG. 10 shows an example of operation performed by theautomatic transmission 1 when the request for the standing start of thevehicle V is made after both the first and second speed position in-gearoperations have been completed, in a case where the shift position SPhas been switched to the drive position D. In the example illustrated inFIG. 10, operations performed before the request for the standing startof the vehicle V is made (operations performed from time t11 to timeimmediately before time t14) are the same as the operations in theabove-described example shown in FIG. 7, and hence operations performedafter the request for the standing start of the vehicle V has been madewill be described, hereinafter.

Referring to FIG. 10, when the request for the standing start of thevehicle V is made (time t15), a required torque TREQ at the time is notlarger than the predetermined value TREF (NO to the step 33 in FIG. 5),and hence the second standing-start clutch control is executed (the step29). With this operation, the degree of engagement of the second clutch6 is progressively increased, whereby the second clutch 6 is completelyengaged, and the first clutch 5 is controlled to the disengaged state.From the above, similarly to the example illustrated in FIG. 9, themotive power of the engine 3 is transmitted to the drive wheels DW viathe second clutch 6 and the second gear mechanism GA2 in a state changedin speed at the transmission gear ratio of the second speed position.Further, along with the above-described control of the first and secondclutches 5 and 6, the second clutch oil pressure PO2 is progressivelyincreased beyond the predetermined pressure PREF, and the first clutchoil pressure PO1 continues to be held at the disengagement pressurePREL.

Further, the correspondence between various elements of the presentembodiment and various elements of the invention is as follows: Theengine 3 in the present embodiment corresponds to a prime mover in thepresent invention, and the third speed synchronization mechanism 16, thefifth-seventh speed synchronization mechanism 17, the first speedsynchronization mechanism 18, the second speed synchronization mechanism25, the fourth-sixth speed synchronization mechanism 26, the gearactuator 53, and the ECU 2 in the present embodiment correspond to aconnection/interruption device in the present invention. Further, theshift position sensor 65 in the present embodiment corresponds to shiftposition-detecting means in the present invention, and the acceleratorpedal opening sensor 66, the brake switch 67, and ECU 2 in the presentembodiment correspond to determination means in the present invention.Furthermore, the ECU 2 corresponds to control means and requiredtorque-calculating means in the present invention, and the lubricatingoil supply system 80 and the ECU 2 in the present embodiment correspondto a lubricating oil supply system in the present invention.

As described above, according to the present embodiment, theconnection/disconnection mechanism provided in the first and second gearmechanisms GA1 and GA2 executes the first, third, fifth, and seventhspeed position in-gear operations, whereby the respective transmissionsof the motive power from the first gear mechanism GA1 to the drivewheels DW, using the first, third, fifth, and seventh speed positions,are connected, and the transmissions of the motive power aredisconnected by executing the first disconnection operation. Further,the connection/disconnection mechanism executes the second, fourth, andsixth speed position in-gear operations, whereby the respectivetransmissions of the motive power from the second gear mechanism GA2 tothe drive wheels DW, using the second, fourth, and sixth speedpositions, are connected, and the transmissions of the motive power aredisconnected by executing the second disconnection operation.

Further, as described with reference to FIG. 5, when the shift positionSP is at the parking position P or the neutral position N, the first andsecond clutches 5 and 6 are disengaged, whereby the engine 3 isdisconnected from the first and second gear mechanisms GA1 and GA2.Furthermore, as described with reference to FIG. 4, when the shiftposition SP has been switched from the parking position P or the neutralposition N to the drive position D or the sport position S, the firstand second speed position in-gear operations are executed, wherebytransmission of the motive power from the first and second gearmechanisms GA1 and GA2 to the drive wheels DW is connected. Further, inthe case where the shift position SP has been switched to the driveposition D or the sport position S, when it is determined that therequest for the standing start of the vehicle V has not been made by thedriver, i.e. during stoppage of the vehicle V, the engagement of thefirst and second clutches 5 and 6 which have been in the disengagedstate theretofore is permitted after completion of the above-describedfirst and second speed position in-gear operations, i.e. afterconnection of transmission of the motive power from the first and secondgear mechanisms GA1 and GA2 to the drive wheels DW has been completed.In other words, the engagement of the first and second clutches 5 and 6is inhibited up to completion of the first and second speed positionin-gear operations.

With this operation, during stoppage of the vehicle V, neither of thefirst and second speed position in-gear operations is executed during orafter completion of an engagement operation of one of the first andsecond clutches 5 and 6. Therefore, it is possible to avoid execution ofthe first and second speed position in-gear operations in a state wherea large differential rotation is generated between portions of the firstand second gear mechanisms GA1 and GA2, connected to the engine 3, andportions of the two gear mechanisms GA1 and GA2, connected to the drivewheels DW, which in turn prevents vibration from being caused byexecuting the first and second speed position in-gear operations,thereby making it possible to improve marketability.

In this case, the first and second speed position in-gear operations areexecuted beforehand when the shift position SP has been switched to thedrive position D or the sport position S. Further, the second speedposition for the standing start of the vehicle V is selected as a speedposition used in the second speed position in-gear operation. From theabove, at the subsequent standing start of the vehicle V, torque of theengine 3 can be transmitted to the drive wheels DW quickly via one ofthe first and second clutches 5 and 6 and an associated one of the firstand second gear mechanisms GA1 and GA2, and therefore it is possible toobtain excellent startability of the vehicle V. As described above, itis possible to cause the first and second clutches 5 and 6 and theconnection/disconnection mechanism to properly operate during stoppageof the vehicle V, thereby making it possible not only to preventvibration and improve marketability but also to obtain excellentstartability of the vehicle V.

Further, when the shift position SP has been switched to the driveposition D or the sport position S, the first speed position with atransmission gear ratio larger (on a lower-speed side) than that of thesecond speed position is selected as the speed position of the firstgear mechanism GA1. With this operation, the increasing degree of torqueby the first gear mechanism GA1 becomes larger than that of torque bythe second gear mechanism GA2. Further, when the shift position SP hasbeen switched to the drive position D or the sport position S, and alsoit is determined that a request for the standing start of the vehicle Vhas been made by the driver, when the first and second speed positionin-gear operations have been completed, one of the first and secondclutches 5 and 6 is selected based on the required torque TREQ, and theselected one of the clutches is engaged, whereas the other clutch isdisengaged. With this operation, at the standing start of the vehicle V,the torque of the engine 3 can be transmitted to the drive wheels DWusing one of the first and second gear mechanisms GA1 and GA2,associated with the selected one of the clutches, in a state in whichthe engine torque is increased to meet the required torque TREQ.

Furthermore, the clutch lubricating oil supply amount, which is theamount of lubricating oil supplied to the first and second clutches 5and 6, is changed by the lubricating oil supply system 80. In this case,the target lubricating oil supply amount QLOBJ, which is the targetvalue of the clutch lubricating oil supply amount, is set to the firstpredetermined amount QREF1 when one of the first and second clutches 5and 6 is engaged, whereas when the first and second clutches 5 and 6 aredisengaged, the target lubricating oil supply amount QLOBJ is set to thesecond predetermined amount QREF2, and this second predetermined amountQREF2 is set to a value smaller than the first predetermined amountQREF1. As a consequence, when the first and second clutches 5 and 6 areboth disengaged, the clutch friction can be suppressed, so that it ispossible to prevent vibration from being caused by executing the firstand second speed position in-gear operations.

Note that the present invention is by no means limited to the embodimentdescribed above, but can be practiced in various forms. For example,although in the above-described embodiment, the first speed position ofthe first gear mechanism GA1 is implemented by the planetary gear unit7, it may be implemented by a first speed drive gear fixed to one of thefirst input shaft 11 and the output shaft 30, and a first speed drivengear rotatably provided on the other of the first input shaft 11 and theoutput shaft 30. Further, although in the above-described embodiment,the output shaft 30, the second-third speed driven gear 31, thefourth-fifth speed driven gear 32, and the sixth-seventh speed drivengear 33 are shared by the first and second gear mechanisms GA1 and GA2,they may be separately provided for the respective first and second gearmechanisms GA1 and GA2. Further, in this case, a second speed drivengear may be rotatably disposed without being fixed to an output shaft ofthe second gear mechanism, and may be connected by the second speedsynchronization mechanism, and the second speed drive gear may be fixedto the second input shaft. The same applies to a third speed drivengear, the third speed drive gear, a fourth speed driven gear, the fourthspeed drive gear, a fifth speed driven gear, the fifth speed drive gear,a sixth speed driven gear, the sixth speed drive gear, a seventh speeddriven gear, and the seventh speed drive gear.

Furthermore, although in the above-described embodiment, the first,third, fifth, and seventh speed positions are set as the speed positionsof the first gear mechanism GA1, and the second, fourth, and sixth speedpositions are set as the speed positions of the second gear mechanismGA2, a plurality of other suitable speed positions may set. Further,although in the above-described embodiment, gear mechanisms of a typewhich connects gears to a shaft using a synchronization mechanism areused as the first and second gear mechanisms GA1 and GA2, any othersuitable gear mechanisms, such as gear mechanisms each formed by acombination of a plurality of planetary gear units and brakes, may beemployed insofar as they are capable of transmitting input motive powerto the drive wheels DW in a state in which the speed of the motive poweris changed at a transmission gear ratio of one of a plurality of speedpositions.

Further, although in the above-described embodiment, the first andsecond clutches 5 and 6 are wet multiple-disc clutches, they may bereplaced by dry multiple-disc clutches or electromagnetic clutches.Further, although in the above-described embodiment, after the first andsecond speed position in-gear operations have been completed, if therequest for the standing start of the vehicle V has not been made by thedriver, the second clutch 6 is engaged (in a half-clutch state) and thefirst clutch 5 is held in the disengaged state, this is not limitative,but inversely to the above, the first clutch 5 may be engaged with thesecond clutch 6 being held in the disengaged state. Furthermore,although in the above-described embodiment, the engine 3, which is agasoline engine, is used as the prime mover in the present invention, adiesel engine, an LPG engine, or an electric motor may be used. Further,it is possible to modify details of the construction of the embodimentsas required within the spirit and scope of the present invention.

It is further understood by those skilled in the art that the foregoingare preferred embodiments of the invention, and that various changes andmodifications may be made without departing from the spirit and scopethereof.

What is claimed is:
 1. An automatic transmission for transmitting motivepower of a prime mover to drive wheels of a vehicle in a state in whicha speed of the motive power is stepwise changed, comprising: a firstgear mechanism that is connected to the prime mover and the drivewheels, for transmitting the motive power of the prime mover to thedrive wheels in a state in which the speed of the motive power ischanged at a transmission gear ratio of one speed position of a firstspeed position group composed of a plurality of speed positions; a firstclutch that is engaged/disengaged to thereby connect/disconnect betweenthe prime mover and said first gear mechanism; a second gear mechanismthat is disposed in parallel with said first gear mechanism, and isconnected to the prime mover and the drive wheels, for transmitting themotive power of the prime mover to the drive wheels in a state in whichthe speed of the motive power is changed at a transmission gear ratio ofone speed position of a second speed position group composed of aplurality of speed positions; a second clutch that is engaged/disengagedto thereby connect/disconnect between the prime mover and said secondgear mechanism; control means for controlling said first and secondclutches; a single connection/disconnection device that is provided forboth of said first and second gear mechanisms, and is capable ofexecuting a first connection operation for selecting one speed positionfrom the first speed position group and connecting transmission ofmotive power from said first gear mechanism to the drive wheels, usingthe selected one speed position, a first disconnection operation fordisconnecting the transmission of the motive power, a second connectionoperation for selecting one speed position from the second speedposition group and connecting transmission of motive power from saidsecond gear mechanism to the drive wheels, using the selected one speedposition, and a second disconnection operation for disconnecting thetransmission of the motive power; shift position-detecting means fordetecting a shift position of a shift lever selectively operated by adriver of the vehicle to one of a plurality of shift positions includinga non-traveling position for stoppage of the vehicle, and a forwardtravel position for forward travel of the vehicle; and determinationmeans for determining whether or not a request for a standing start ofthe vehicle has been made by the driver, wherein when the detected shiftposition is at the non-traveling position, said control means disengagessaid first and second clutches, wherein thereafter, when the shiftposition is switched from the non-traveling position to the forwardtravel position, said connection/disconnection device executes the firstand second connection operations, and in the second connectionoperation, selects a predetermined standing start speed position for thestanding start of the vehicle from the second speed position group,wherein in a case where the shift position is switched to the forwardtravel position, when both the first and second connection operationshave been completed, said control means permits engagement of said firstand second clutches, and wherein in a case where the engagement of saidfirst and second clutches is permitted, when the request for thestanding start of the vehicle has been made by the driver, said controlmeans selectively engages one of said first and second clutches.
 2. Theautomatic transmission according to claim 1, wherein saidconnection/disconnection device selects a speed position with atransmission gear ratio larger than a transmission gear ratio of thepredetermined standing start speed position, from the first speedposition group, as a speed position for use in the first connectionoperation executed when the shift position has been switched to theforward travel position, the automatic transmission further comprisingrequired torque-calculating means for calculating a required torquerequired for the drive wheels, wherein in a case where the engagement ofsaid first and second clutches is permitted, when the request for thestanding start of the vehicle has been made by the driver, said controlmeans selects and engages one of said first and second clutches anddisengages the other of said first and second clutches, based on thecalculated required torque.
 3. The automatic transmission according toclaim 1, wherein said first and second clutches are formed by wetclutches that use lubricating oil, the automatic transmission furthercomprising a lubricating oil supply system that supplies the lubricatingoil to said first and second clutches, and is capable of changing alubricating oil supply amount, which is an amount of the lubricating oilsupplied to said first and second clutches, wherein when one of saidfirst and second clutches is engaged, said lubricating oil supply systemsets the lubricating oil supply amount to a first predetermined amount,whereas when both of said first and second clutches are disengaged, saidlubricating oil supply system sets the lubricating oil supply amount toa second predetermined amount smaller than the first predeterminedamount.
 4. The automatic transmission according to claim 2, wherein saidfirst and second clutches are formed by wet clutches that uselubricating oil, the automatic transmission further comprising alubricating oil supply system that supplies the lubricating oil to saidfirst and second clutches, and is capable of changing a lubricating oilsupply amount, which is an amount of the lubricating oil supplied tosaid first and second clutches, wherein when one of said first andsecond clutches is engaged, said lubricating oil supply system sets thelubricating oil supply amount to a first predetermined amount, whereaswhen both of said first and second clutches are disengaged, saidlubricating oil supply system sets the lubricating oil supply amount toa second predetermined amount smaller than the first predeterminedamount.